the mystery 'deepens'............
Although it isn’t officially named
as such, I tend to call the Lightroom edit space Lightroom RGB. Mark Hamburg had suggested it might be more appropriate to call it “bastard- ized RGB” since the space is using ProPhoto RGB chromaticities, but with a gamma of 1.0 instead of 1.8.
If you're implying that there's something wrong with using PPRGB primaries but not the PPRGB TRC, or even that there's something unusual about doing internal image calculations in a linear space, I don't agree.
Whenever I write color image processing code that uses the primaries of any RGB color space, I always do the internal calculations in a linear representation, with nominal black equal to zero, nominal white equal to one, and double precision floating point.
There are a lot of advantages to this. The calculations are more straightforward. The code is easier to read. You can allow intermediate calculations to exceed nominal white (which is not defined in many nonlinear color spaces), or to be below nominal black, (which is defined in hardly any nonlinear color spaces (PhotoCD Ycc --> RGB excepted).
If you mean bastardized in some other, entirely complimentary way, then I apologize for wasting your time with this post.
Jim